RUN Domain Containing Protein 3A (RUNDC3A)

RUNDC3A is expressed as a 50-kD cytosolic protein, whereas the deduced 400-amino acid isoform is expressed as a 45-kD protein; both were found in mouse brain. Sequence analysis predicted that RPIP8 is a hydrophilic protein that shares 94% identity with the mouse sequence. RPIP8 lacks transmembrane or leader regions but contains 7 heptad repeats characteristic of coiled-coil domains and 3 potential phosphorylation sites. Mutation and GST pull-down analyses indicated that integrity of the N-terminal two-thirds of RPIP8 is necessary for interaction with RAP2A. Northern blot analysis of mouse tissues revealed that RPIP8 is expressed as a 2.2-kb transcript in brain, as a 3.0-kb transcript in liver and kidney, and as 3 transcripts, including a 1.4-kb major transcript, in testis.